ANATOMY - RADIOGRAPHY The Skull.—An instructive radiogram of the skull is obtained by placing the tube generating the rays on one side of the head and by laying the photographic plate flat against the other. Fig. I on plate shows a lateral view of the head resting upon the upper part of the spinal column. A good view is obtained of the extent of the cavity which contains the brain. The orbital and nasal chambers with their accessory air sinuses (antrum of Highmore and sphenoidal air sinus) are well seen. Particularly there is noticeable, immediately behind the sphenoi dal sinus, the saddle-shaped sella turcica for the lodgment of the pituitary gland.
Shoulder.—A front view of the shoulder and neighbouring part of the chest when the arm hangs by the side of the body, dis closes the relative position of the bones of that region. The ribs pursue an obliquely downward course and their movements in life are well seen.
The clavicle passes outwards and slightly upwards toward the acromion process of the scapula, with it to form a bony arch overhanging the shoulder joint and thus helping to prevent upward displacement of the humerus at that joint. The body of the scapula rests on the ribs thickening at its axillary border and upper and outer angle where it expands to form the glenoid fossa for reception of the head of the humerus. The coracoid process which is swung by fibrous tissue to the clavicle in the recent state is very evident.
The ball and socket character of the shoulder-joint is so ar ranged as to allow of extensive movement of the arm at the joint, the socket (glenoid cavity) being small as compared with the large articulating surface of the ball. The upper extremity of the humerus with its articular surface and tuberosities are well seen.
Elbow.—A good picture of this region is obtained by taking a radiograph from its inner side with the elbow-joint slightly bent and the forearm in such a position that the palm of the hand is directed toward the median plane of the body. The lower end of the humerus shows the internal condyle with a ridge running upward and a groove behind for the passage of the ulnar nerve from the arm into the forearm. The upper end of the ulna shows the deep concavity by which it articulates with the pulley shaped surface of the humerus and its helmet-shaped upward extension (olecranon process) for the attachment of the triceps muscle. The head of the radius supported upon its conical neck articulates with the humerus above and the ulna at the side. The whole picture emphasizes the hinge-like character of the elbow-joint and the pivot character of the joint between the bones of the forearm at the elbow.
Wrist and Hand.—Fig. 5 on plate shows the lower part of the forearm and hand viewed from the palmar aspect. The radius and ulna, the carpal, metacarpal and phalangeal bones form distinct shadows. The outline of the wrist-joint shows that the hand is supported mainly by the expanded lower end of the radius, the head of the ulna being separated from the carpus by an interval which in the recent state is filled up by a fibrocarti laginous pad.
The outlines of all the eight bones of the carpus can clearly be made out forming a group consisting of two rows of bones with an .-shaped joint between them. The os magnum is the largest bone of the group arid lies with its long axis in line with the middle finger, the semi-lunar and the radius. Its rounded head fits into a cup formed by the scaphoid and semi-lunar; its body is flanked by the trapezoid and unciform, and its base sup ports the third and to a lesser degree the second and fourth metacarpal bones. The pisiform is rather indefinitely seen imme diately below the ulna and in front of the cuneiform. The trapezium partially hides the trapezoid.
The four inner metacarpal bones lie close to one another, while the first or that of the thumb is separated from the second by a wide interval. A small sesamoid bone is seen lying upon the inside of its head.
The phalanges of the fingers and thumb are shown very dis tinctly, and the ball and socket character of the metacarpopha langeal and the hinge-like nature of the inter-phalangeal joints are also manifest.
Pelvis and Hip-joint.—The architecture of the bony frame work of the pelvis which transmits the weight of the trunk and upper extremities allowing at the same time room for viscera is well seen in fig. 6 on plate.
The relation of the wedge-shaped sacrum with its coccygeal appendage to the rest of the body girdle is apparent. The sacrum is seen to be interlocked between the ilia of the innominate bones, so as to form with them an arch transmitting the superincumbent weight either to the lower extremity in the erect position or to the ischial tuberosity in the sitting position. The tendency towards the spreading of the arch is prevented by the front portions of the pelvic girdle acting as tie beams, and there are three "buffers" which break shocks, one at the symphysis pubis in the middle of the front part of the girdle, and the other two at joints between the sacrum and ilia. The foramina for the exit of nerves from the spinal cord to supply the lower extremities and soft parts of pelvis are apparent. The general character of the female as compared with the male pelvis is well exemplified in fig. 6; e.g., the widely spreading ilia, the great width of cavity below the ilia and the wide sub-pubic angle.
To get a good radiogram of the region of the hip-joint is a somewhat difficult matter. One taken from the front shows the thigh occupying its position in the erect posture, revealing the socket or acetabulum, the head of the femur with its pit for the round ligament, the oblique neck, and the upper part of the shaft with the great and small trochanters. The arrangement of the cancellous bone tissue is such as to bear the superincumbent weight in the best possible way.
Knee.—A good general idea of the region is obtained by taking a radiogram from the side (fig. 2 on plate). It shows the lower part of the femur with its condyles, upper part of the tibia with its spine, tuberosities and tubercle, and the upper part of the fibula with its head.
There is seen to be but little interlocking between the femur, tibia and patella, which enter into the formation of the knee joint. The tibia articulates by a relatively small surface with the relatively large articular surface of the femur, the joint so formed being an example of a hinge joint with the pin of the hinge a movable one. The spine of the tibia is seen projecting upward between the condyles of the femur acting like the flange of a wheel and so helping to prevent lateral displacement of the tibia from the femur at the joint. The knee-cap, to which are attached the great extensor muscles of the leg, moves upward and down ward on the femur only. The fibula is seen articulating with the tibia, the joint surface being oblique in direction in order to break shocks between the two bones.
Ankle and Foot.—In fig. 4 on plate a view of the skeleton of the lower part of the leg and of the foot is given from the inside. The tibia and fibula of the leg, and the tarsal and metatarsal and some of the phalangeal bones are shown.
The tibia articulates with the astragalus at the ankle joint, and on close inspection the relative positions of the malleoli of both the tibia and fibula to the astragalus can be made out, the bones of the leg and the astragalus forming a hinge joint. The tip of the outer malleolus formed by the fibula reaches to a lower level than the tip of the inner malleolus, which belongs to the tibia.
The antero-posterior and to a less extent the transverse arch of the foot are shown, the pillars of the former consisting of the great tuberosity of the os calcis behind and of the heads of the metatarsal bones in front. The astragalus forms the keystone of the arch, and transmits the weight of the body from the tibia to the astragalus and os calcis behind, and to the scaphoid, cuboid, cuneiform and metatarsal bones in front. The spicules of the cancellous tissue in these bones are arranged so as to bear the weight of the body transmitted through them. The so-called tunnel of the tarsus and the mediotarsal joint across the foot between the astragalus and os calcis behind and the scaphoid and cuboid in front are very apparent, showing at the same time that the articulation between the os calcis and cuboid forms a separate joint. The front of the middle cuneiform is indicated by a narrow vertical shadow situated a little behind the shadow indi cating the anterior border of the internal cuneiform.
The radiogram illustrates vividly the essential difference be tween the hand and the foot, in that the big toe is seen to be closely applied to the second toe and not opposable to the rest of the foot as the thumb is to the rest of the hand.
Ossi fication.—Ossification begins in each bone of the skeleton at one or more spots called "primary centres of ossification." Each appears before birth and by their spreading they form the main part of the bone. After birth "secondary centres of ossi fication" begin to show themselves independently of the main mass, form what are known as "epiphyses" and join it at various periods after birth to make the adult bone. Radiography, when applied to the living body, affords information as to the forms, times of first appearance and times of junction of the epiphyses with the main parts of bones to which they belong. It has shown that there is very great variability in the times, appearance and fusion of epiphyses in different individuals.
Thorax and its Contents.—Apart from revealing the skeleton of the thorax, radiography permits inspection of the position and contour of the heart and great vessels, the lungs and mediastinum.
Abdomen and its Contents.—Subsequent to the introduction of matter opaque to X-rays such as barium or bismuth salts into certain organs, radiography has played an important part in elu cidating the anatomy of the alimentary canal and urinary tract.
Fig. 3 on plate shows a normal stomach and first part of the duodenum immediately after the ingestion of a barium meal. The clear area at the upper part indicates the air-containing por tion of the cavity in the neighbourhood of the entrance of the oesophagus.
The writer of this article is indebted to Dr. Levack, Radiologist, Royal Infirmary, Aberdeen; Dr. Spriggs, Duff House, Ruthin Castle, North Wales; and Dr. Salmond, Radiologist, University College hospital, London, for the radiograms that are reproduced in Figs. I to 6.